Production of oil



July 31, 1945. W VG; 5R15 PRODUCTION OF OIL Filed Sept.v 16, 1943 Mfo/v6. f/f.

5% ATTORNE s Patented July 31,'1945 vUNITED STATES PATENT Vorifice y l y:ascesa PRODUCTION F Olli..

Wilson G. Bris, Napoleonville, La., assignor to The Texas Company, NewYork, N. Y., a corporation of Delaware Application 'september 16, 1943,'segni No. tosses 7 Claims. (Cl. 1034-232) pumping crude oil tending todeposit paraflln wherebyproduction ofv the oil is accomplishedcillciently and the deposition of paraiiln is re; duced or prevented. i

When the vnatural ilow of crude oil from a well has ceased or become tooslow for economical production, articial production methods areemployed, and in many cases, it is advantageous,

, at least during the ilrst part of the artiilciai pro duction period,to employ gas lift. NumerousV types of equipment for producingoil by gaslift are available, but they all rely upon the same general principlesof operation. In the usual case, dry Gas consisting essentially ofmethane and ethane is forced down the annulus between the tubingandthecasing and into the oil in the tubing. As the oil in the tubingbecomes aerated with gas, the density of the oil decreases, andveventually the weight of the column of aerated oil in the tubingbecomes less than the pressure exerted on the body of oil in the well.and ilow of oil occurs at the surface. While in some cases the dry gasmay be introduced through the tubing so as to cause production throughthe annulus, this is not preferred unless special conditions arePresent.

It has been recognized that gas-lift methods for producing crude oil areof questionable value when un ou tends to deposit params. 'rms isbecause it has been found that vparaiiln deposition in a gas-lift wellis particularly heavy. Accordingly, it has been frequently been decidednot to use gas-lift methods because the expense of controllingparamndeposition would more than. offset' any advantages obtained through theuse of these methods.

An important problem encountered in producing a well by gas lift arisesin starting the ilow of oil. The gas-lift systems available on themarket generally comprise an arrangement of valves in the tubing wherebythe gas may be introduced nrst into the'upper part of the column of oilin the tubing and then at lower points so that it is not necessary toraise the entire column of oil in the tubing a substantial distanceprior to the mixture oi the gas with the oil. `'I'hese systems of gaslift satisfactorily accomplish the object of lessening the problem ofstarting production. When the crude oil being produced tends ao depositparamn, however, the presence of the, valves makes the Job of cleaningparailln from the tubing more dlilicult.

With the foregoing problems'in mind. it is a principal object of thepresent invention to provide a method of producing crude oil tending todapositfparaillncby gas lift, whereby the oil may be producedetiiciently, while. at the same time,

the deposition of parailln is reduced or prevented.

Other objects of the invention will in part be obvious and will in partappear hereinafter. I have discovered in accordance with the inventionthat crude oil tending to deposit par can be produced by gas lift whileavoiding troubles due to paralln deposition, provided a gas is uti lizedwhich contains .light hydrocarbons dispersed therein in the liquidphase. As pointed out above, the dry gas which is conventionally used iscomposed essentislly ol' methane and ethane, and any small amountlofothcr hydrocarbons that may be present inthe gas are in the vaporphase under the conditions at which' the dry sas is employed for gaslift. In the method of the invention, l employ a mixed uld whichcomprises an amount of liqueflable hydrocarbons such that an importantproportion of these hydrocarbons are present in the liquid form underthe pressure and temperature conditions existing at the time of gaslift; the particular amount required for the desired reduction orprevention of parailln deposition being dependent upon the specicconditions of production in the oil well and the characteristics of theliqueilable hydrocarbons.-

, The liqueable hydrocarbons'may vary in composition; for example,hydrocarbon mixtures such as a petroleum ether or light naphtha fractionof petroleum, natural gasoline, and hydrocarbons otherl than methane andethane present in a fluid owed from a distillate or condensate well maybe employed as the liquid phase material in the gas. Thus, thehydrocarbons in the gas, other than methane and ethane, preferablycomprise hydrocarbons containing not more than 8. parv tlcularly from 4to 8, and especially from 3 to 8 carbon atoms. The dispersed liquidhydrocarbons may and usually will also include heavier hydrocarbons.Hydrocarbons containing 3 or more carbon atoms are conventionallyreferred to as liquefiable hydrocarbons, because, although thee` lightermembers such as the C: and C4 hydrocarbons may be gases imderatmospheric conditions. they can be obtained in liquid form from a wet'gas suchv as a distillate iluid by conventional recovery methods. f

The method of the invention may be practiced in various ways. The liquidhydrocarbons which it is desired to have present in the ses may beinjected intotheusualdrygastobeusedingas lift, preferably in such manneras to eilect dis-- persion of the liquid hydrocarbons throughout thegas. This may .be accomplished by any conventional means. For example.the liquid hydrocarbons 'may be injected through an aspirator nozzleinto the gas at the pressure required in the sas-lift operation. The drygas may be gas viroxn a natural gasoline plant which has been compressedto the desired pressure. gas from a high-pressure gas well, or residuegas from a distillate recovery plant. Gases of the latter typesordinarily will be at a sufliciently high pressure to permit their beingused without compression.

When practicing the method in this way, the

liquid hydrocarbon mixture employed may be any a of the classes ofmixtures referred to above. Itis preferred to use a mixture of` thistype which contains a substantial proportion of propane and butanes inadditionto the other hydrocarbons normally includedin suchl mixtures.Thus, if natural gasoline or distillate is used as the liquidhydrocarbon mixture, it is preferred that it not be subjected toweathering, which would permit evolution of propane and butanes.

I have found that the method or the invention can be carried out in aparticularly effective manner in areas where suitable wells areavailable by ing the pressure and temperature of a distillate fluid,substantial condensation of liquelable hydrocarbons occurs due .to thephenomenon of retrograde condensation and also the normal temperatureeffect. The pressures required for gas lift operations are such thatsubstantial condensation. of liqueable hydrocarbons occurs on reducingthe pressure on a distillate fluid to the pressure of gas lift, andthese condensed liqueable hydrocarbons will include propane and butanesas well as higher boilinghydrocarbons. A distillate fluid is usuallyemployed in accordance with the invention by flowing the fluid from adistillate iormation, reducing the pressure on the fluid by means of apressure-reducing valve located either at the surface or in thedistillate well to the pressure of gas lift, and then passing theresulting iiuid containing dispersed liquid hydrocarbons into the wellor wells to be produced by gas lift. Y

The manner in which the invention may be practiced utilizing adistillate .fluid is illustrated in the accompanying drawing in whichthe single gure is a moreor less diagrammatic view, partly in section,showing an oil well, surface equipment, and a distillate well utilizedin causing fiow of the oil well.

Referring to the drawing, the weil A is an oil well producing crude oiltending to deposit parafn, and the well B is a distillate well whichproduces a duid at a high pressure within the retrograde condensationrange of the constituents of the casing, a standing valve Il. a bullp1ug'20.`

and three valves 22, 24, and 28. which furnish communication between theannular space above the packer and interior of the flow tubing. Thesevalves are controlled by a cylindrical bar (not showni'disposed inthetubing-which may be raised and 4lowered from .the surface by means ofawire 2l which is operated by any suitable assenso means not shown.' Thebar, on being placed opposite a valve, opens that valve. In thearrangement shown, valves 22 and 24 are starting valves, and the valve2B is a now valve.

When the system disclosed'is in regular operation, the distillate fluidis flowed from .the well sulting mixed fluid is flowed into the annularspace between the casing and the tubing andperiodically Vis permitted topass vinto the flow tubing through-valve 26, this valve being opened andclosed at regular intervals to permit the alternate lling of the tubingwith oil and the flow of oil to the surface by means of the gas lift. Bythe arrangement shown, the distillate fluid containing the dispersedliquefied hydrocar-` bons enters the crude oil and functions to lift theoil to the surface, while, at the same time, reducing or lpreventing thedeposition of paraiiin.

The useof a distillate uid in practicing the present process has otheradvantages. The liquefiable hydrocarbons present in the distillate fluidare absorbed in the crude oil so that the liquid product from thedistillate well and the crude oil `from the oil well may be handledemciently in one stream. There is. no loss of light components sinceafter the crude oil has been passed through a conventional separator.the gases obtained may be treated in a natural gasoline plant forrecovery of liqueilable constituents.

Distillate nuids vary in composition, but they are all characterized inthat they contain a substantial proportion of hydrocarbons containing 3to 8 carbon atoms and in that an important proportion of thesehydrocarbons are in the liquid phase at the pressure and temperatureconditions of gas lift. In starting gas-lift operations it is sometimesnecessary initially to employ pressures as high as 1500 pounds persquare inch, but after contain more liquid phase material at higherpressures, at pressures of the order of 500 pounds per square inch andat atmospheric temperatures, they still contain important amounts ofliquid phase material. A representative distillate fluid was found tohave the following composition:

Component Mol. fraction Methane 0. 95173 Ethane 0. 01219 Propane.-.0.046 Isobutane.. 0. 00274 n-Butane. 0. 00352 Iso-pantano. 0. 00171n-Pentane 0. 00109 Hexanes. 0.001112 Eeptanes. 0. 00241 Gctanes andheavle 0.00016 Carbon dioxide 0. (D491 In the well frm which this fluidwas flowed.

the bottom hole pressure was about 5000 pounds atmospheric temperatureand pressure, whereby but that at soo4 pounds per square meh the num at40 F. had a liquidvolume of 0.00198 cubic foot per pound and at 100 F. aliquid volume of l 0.00154 cubic foot per pound.

A The method of theinvention has been practiced three dollars per month.A conventional gas-lift system was installed when the flow ceased. Thegas for gas lift was obtained from a distillate well in the vicinity,and the entire distillate fluid was introduced into the oil well. Thepressure on the distillate fluid was reduced to about 500 pounds persquare inch by means of a valve in the distillate well. This reductionin pressure and concomitant reduction in temperature caused substantialcondensation of liquid hydrocarbons, tests showing that at the rate thewell was flowed about 2.40 barrels of liquid hydrocarbons werebeingintroduced into the oil well during each 24 propane through octanesand heavier.

The oil Well was produced at a rate of about 45 barrels per day for anextended period and no difliculties due to parain deposition wereexperienced. Inasmuch as i1; would normally be expected that whenplacing a well on gas lift, paraffin troubles would increase rather thandecrease, this result indicates that the present method represents animportant step forward in the production of crude oils tendingto depositparaii'ln by gas-lift procedures.

It will be understood that the amount bf liquid hydrocarbons required tobe used will vary in each case/depending upon `the type of crude oil,equipment in the well, depth of the well and other factors. Accordingly,this amount should be determin'ed by tests in each case. Informationobtained in developing the present invention has indicated that when anordinary distillate fluid is used, an excess of liquid hydrocarbons willbe present, This, of course, is not a disadvantage because the excess isrecovered along with the crude oil. For example, tests have indicatedthat in the above Well a uid containing an amount of liquid phasematerial corresponding to 5 to 10 gallons per 24 hour period would besatisfactory. Although when the production from a distillate well isused in the process, there will usually be present more than enoughliquid phase materiaLto accomplish the objects of the invention, it willbe understood that in a case in which this liquid phase material isinsuflicient additional liquid hydrocarbons may be added. l

Obviously many modications and variation of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof, and therefore only such limitations should be imposedas are indicated in the appended claims.

I claim: v

1. lIn the process of producing from asubsurface reservoir by gas lift acrude oil tending, to deposit paraili'nl the improvement which comprisesintroducing from the surface into an oil well tap-v Ping the crude oilreservoir, under the pressure required for gas lift, a mixed fluidcomprising a gas and liqueable hydrocarbons in the liquid phasedispersed in said gas, said liqueable hydrocarbons comprising asubstantial proportion of hydrocarbons which are in the liquid phase atthe crude oil is aerated and is caused to iiow to the surface whileavoiding substantial deposition of paraffin.

2. In the process of producing from a subsurface reservoir by gas ylifta crude oil tending t0 deposit paratlin, the improvement which comprisesintroducing from the surface into an oil well tapping the crude oilreservoir, under the pressure required for gas lift, a mixed iiuid`comprising a gas and liquefiable hydrocarbons in the liquid phasedispersed in said gas, said liquefiable hydrocarbons comprisinghyrocarbons containing not more than 8 carbon atoms and a substantialproportion ofhydrocarbons which are in the liquid phase at atmospherictemperature and pressure, and being present in amounts suicient toprevent substantial deposition of paraffin in the well, whereby thecrude oilv in the well is aerated and caused to flow to the surfacewhile avoiding substantial deposition of parain.

3. In the process of producing from a subsurface reservoir by gas lift acrude oil tendingto depositv parafiin, the improvement which comprisesintroducing from the surface into an oil well tapping the crude oilreservoir, under the pressure required for gas lift, a mixed fluidcomprising a gas and liqueable hydrocarbons in the liquid phasedispersed in said gas, said liqueable hydrocarbons comprisinghydrocarbons containing 3 to 8 carbon atoms and a substantial proportionof hydrocarbons which are in the liquid phase at atmospheric temperatureand pressure, and being present in amounts suiiicient to preventsubstantial deposition of parain in the well, whereby the crude oilinthe Well is aerated and caused to w to the surface while avoidingsubstantial deposition of parafn.

4. In the process of producing from a subsurface reservoir by gas lift acrude oil tending to deposit paraffin, the improvement which comprisesintroducing from the surface into an oil well tapping the crude oilreservoir, under the pressure required for gas lift, a mixed iluidcomprising a gasl and liqueable hydrocarbons in bon atoms, whereby thecrude oil in the well is aerated and caused to flow to the surface whileavoiding substantial deposition of paraiiin.

5. In the process `of producing from a subsurface reservoir by gas lifta crude oil tending to deposit paraiiin, the improvement which comprisesintroducing from the surface into an oil well tapping the crude oilreservoir, under the pressure required for gas lift, a mixed uidcomprising a gas and liqueable hydrocarbons in the liquid phasedispersed in said gas, said liquefiable hydrocarbons comprisinghydrocarbons containing not more than 8 carbon atomsand a substantialproportion of hydrocarbons which are in the liquid phase at atmospherictemperatureA and pressure, and being present in amounts suilcient toprevent substantial deposition of paraffin in the well, said mixed fluidbeing obtained by mixing with a gas comprising normally gaseoushydrocarbons a hydrocarbon mixture in liquid phase recovered from a uidowed from a well tapping a distillate formation, whereby the crude oilin the well is aerated and caused to ow to the surface while avoidingsubstantial deposition of parailln 6. In the process of producing from asubsurface reservoir by gas lift a crude oil tending to deposit parain,the improvement which comprises`introducing from the surface into anoil` well tapping the crude oil reservoir, under the pressure requiredfor gas lift, a uid which com prises the production from a well tappinga distillate formation and consists of a mixed fluid comprising normallygaseous hydrocarbons in the vapor phase 'and liqueiiable hydrocarbons inthe liquid phase dispersed in said gas, said liquelable hydrocarbonscomprising a substantial proportion of hydrocarbons which are in thliquid phase at atmospheric temperature and pressure, whereby the crudeoil in the Well is aerated and caused to flow to the surface whileavoiding substantial deposition of paramn.

'7. In the process of producing from a subsurface reservoir by gas lifta crude oil tending to deposit paraflin, the improvement which comprisesreducing the pressure on a iiuid owed from a. well tapping a distillateformation from the pressure of the distillate formation to the pressureof gas lift, whereby the distillate iiuid is converted to a mixed fluidcomprising normally gaseous hydrocarbons in vapor phase and liqueablehydrocarbons in liquid phase dispersed in said vapor phase, saidliqueable hydrocarbons comprising a substantial proportion ofhydrocarbons which are in the liquid phase at atmospheric temperatureand pressure, introducing said mixed iiuid into an oil well tapping thecrude oil reservoir, under said pressure of gas liftI whereby said crudeoil is aerated and caused to ow to the surface While avoidingsubstantial deposition of paraffin, said crude oil containing dissolvedtherein liquefiable hydrocarbons of said mixed uid, and recovering saidcrude oil containing said liqueiiablel hydrocarbons of said mixed fiuid.

WILSON G. ERIS.

